Magnetic transducing apparatus utilizing a helical sound trace



Feb. 8, 1949. w. E. BRADLEY 2,461,368

MAGNETIC TRANSDUCING APPARATUS UTILIZING' A HELICAL SOUND TRACE Filed Dec. 19, 1944 Tagli..

INVENTOR l: h//LL/'AM /MDLEY Y I ATTORN EY Patented Feb. 8, 1949 MAGNETIC' TR'NSDUCING APPARATUS UTIILIZI'NG? A HELICA'L SUND'TEACE U William E; Bradley;` Swarthmore Pa., assigner,

by; mesne assignments, to PhilcoCorporatimt,` Philadelphia, Pa., a corporation. of' Pennsylmma Applieaem member 19, 1944; semi Nesssssss 113- oiwims. (01.. 17e- 100m `1 This invention relates. toY sigfnalf transmission systemsandf more' particularly to systems of the Y 'type wherein thesignals arestored as magnetizasirable `because-of the great' compactness of the Wre only@ fewthousandths ofy storage means. an inchx indiameterL isuseable, andy `an hours worth of recording-'can be putin an overcoat pocket. However', roundwire inthe past has vwmecessitated longitudinal' magnetization. There is a limit to thecloseness with which the indi- -vidualmag-nets can be packed on a round wire.

The consecutive :magnets tend to demag-netize leach other. With `transverse magnetization, this demagnetizing tendency is muchles's. 'Iransverse magnetization: has been used in the past successfullyribbon or otherspeeial' shapes which have two great disadvantages. They-are more expensive and require more storage space.

v5inothe-:r'important 'obect ,is 'to prrzovidev a yn'letlfiodianrirmeansfor xnaqgnetizi'ng` a vwireA which isfof "aire-ulm' :orrolmd cross-section, as distinguished from flat or ribbonlike wire, so'that thewdetection or pick-up means for use with the signal-magneti'zed wire is substantially' independent of. the peripheralorentatibn thereof with respect tothe wire. In thel case of Il'at or' ribbon-like wire or any recording wiref which possesses: peripheral homers,- there: is a tendency `for the magnetization -tol bef -noneuniformaround' the peripheral surface of the wire, with theresult-that special means must be provided" "for` insuring proper registration fandorientation :between-one particular-lime of.' the wiresurfaceandV` 'the pick'- up means. While: round'- vcli'rey is more likelyfto. be

'uniformiy-rma'gnetizeci in responsev touniformim- .lpressedffsipnala there isf however the diilioulty` of record by means of transverse magnetizaticmv on wire; because small' twists the` wire, about the wires: ow'rrf axis, produced' `substantial verfaticnainoutput'from the piclt-up head1 For -xamplawintlie wire werefsto twistia-Q'Ofaboutfit's the *signal "would: bei completely-"lost 2 f iy Through the' use ofi a carrierY frequency system and a rotating. recording field ydiilicultys is eliminated. Since the: rotatingamagnetic heldintaies;- asz manytimespertsecond as-therearecycles Yper.` seconclfY vin the. `carrier frequeney,.ziti vWfl-1l be evident thatany possiblev twistin'gfof the :wirewill be negligible Vcornnareii tolthe rotationV of the recorded'. magnetic field. li/loreover, it isfnoflonger necessary that the recordingihead bein anypar.-

tisular initial registry with the. recording om the Wire. Y cording.1 to.` this-invention,;it is possible to: produce uniformi magnetizationsr for. uniionn signaler-.and also to maintain faithfulness in thev signal. translation regardless. of .the :peripheral -Orientationiof the pick-up means with respect lto the wire:

f A feature of invention' relates jto amethod of .signal-"controiled .magnetization of a. rround.` or circular .cross-section; wire, employing ai mag:- netizing iielxi whieh rotates peripherallyaround thewirerfduring recording. v-

Another feature relates tov asignal-controlled magnetizing. arrangement for round: `moss-section wire records; vs'hereiln a plurality' 'oi' mag'- U netizilng members are energized in phase displacement relation fromthefsame signal outputfwhereby the magnetic trace is. substantially helicalE or ofscre'w thread?form.` f

Anotherf'eatnrerelatesto a signal-controlled rnagnetizing arrangement for round orosa-seey tion wire records wherein; a plurality of magnetizing-4 fields are' produced? at' signal-modulated carrier frequency; but spaciallydisplaeed along the wire-approximately* one'fquarter the carrier wavelength tof produce-the effect of a peripheral helical magnetization of the wire. A furtherA feature relates to' an improved magneti'zed wirerecording `system of the mod'illatorY carrier'recordingfand-pick-upltype. i A- 'stll further feature relates 'tov the novel organi'zatlon, arrangement fand relative location *of partewlln'eh vcooperate tioy produce a'n- 'improved g reoordingrsystem of the 'telegraphon'e type..

otnenfeaturesgandf advantages: .not specifi-,cally enumeratedwill` be "apparent 'after a consitier-aa,--

v'tlonfc'if'fthef following detaileii descriptions and' tle appointee-claims. v A 'In the-drawing which iilustratescertain preferred-embodiments,

As 4a Aresult of femployingrtha methodsacg are generated or produced by the device I, may be voice frequency signals, telegraph signals or any other electric signals preferably in the low or voicefreuuency range. These signals are applied to a modulator 2, of any well-known kind which is supplied with a sustained electric carrier wave from the source 3. Source 3 may :be

any suitable electric oscillator customarily em- I Pref- :Surface ofthe recording wire. Wire"| IV is preferably circular or round in cross-section. It

will Vhe understood that the wire'II is of any "wellfknown iron or iron-alloy composition such as employed in telegraphones ormagnetized wires recording systems, as is true also for the composition of themembers 1 to IG. Windings 5, I,

'are so arranged that for the same direction of current iiow'therethrough, the pole pieces are vmagnetized with opposite polarity. i

`Aportion of the modulated carrier output from device 4 is also'applied to a suitable phase delay .network I 2, which'is adjusted so that its signal output is V90" displaced in phase `with respect `to vthe 'output vsignal of device 4. This phase displaced signal is applied to a second pair of field windings I3, I4, wound on respective iron cores I5, I6, having respective curved pole pieces l1, I8, in close proximity to wire II. In accordance Vwith the invention, the pole Vpieces I 1, I8, are arranged at substantially right angles to pole pieces 9, I0, in the same transverse plane and their respective windings I3, I4, are wound so lthat for the same direction of current flow therethrough, the pole pieces II, |8,.are of opposite polarity. Thus, at any given instant, the -four pole pieces are all energized, but because of their spacial displacement around the wire and also lbecause of the 90 phase displacement in the respective magnetizing currents, the wire II is subjected to a rotating iield which rotates at a fixed rate around the longitudinalaxis of the Wire. Since the wire II is moved in the direction Aof itslength, the magnetic trace on the periph- .cry of the wire follows a path.

At vthe receiving station the wire II passes helical or screw thread through a pick-up arrangement comprising, for

example, two magnetic polepieces I 9-20, with corresponding cores 2|, 22, and their individual pick-'up windingse23, 24. The windings 23, 24,

are connected in series andthence to a carrier waveamplier 25, whose output is .a substantial Aelectrical image -of the output of amplifier 4.

Amplifier 25 vfeeds a demodulator orfdetector-26 tation between the pick-up poles I9, 20 and the wire, and the position of the pick-up poles with ,ery thereof.

Instead of relying upon electrical phase displacement to secure the helical magnetic trace, the pole pieces 9, I Il, may be opposite each other in substantially the same" plane; andthe pole pieces II, I8, may be opposite to eachother but displaced along the length of the wire. In accorda-nce with the present invention, this spacial displacement of the two sets of pole pieces is substantially equal to one-quarter of the wave length of the carrier from source 3. Such an arrangement is schematically illustrated in Figs. 2 and 3. With this arran-gement, the poles 9, III, I1 and I8 will be energized all in the same time phase, -for example by being connected in series as shown in Fig. 2.V -Because of the longitudinal movement of the wire and because of the particular spacial displacement of the two sets of poles, the magnetic trace on the wire follows a helical or screw thread path.

While certain particular ways of impressing the signal magnetizations on the recordingwire by means of a rotating vmagnetic eld have been described, othcrwell-known ways of g producing the rotating magneticY eld may be employed,

Aand other changes and modifications .may-'be made without departing from the spirit and scope of the invention. 1 s

`It will be understood tha-tthe receiving pick-up shown in Fig. 1, instead of using asinglepair of pole pieces IS, 2i), located in the same transverse plane, may employ -two pairs of pole1pieces arranged in the same plane asin Fig. l and pro vided with a suitable phase delay network vto correspond with the phase delay at the transmitting recorder. Likewise, the receiving pick-up may use two sets of pole pieces as shown in Figs. 2 and 3, displaced as described. In either of these cases, there is the added advantage that during rewinding of the recording wireat .th receiver, no play-back takes place. 1'

While in the foregoing, reference ,has been made to a modulated carrier for controlling the magnetizations of the recording :wire-it willbe understood that the invention is Vnot limited to Arecording of signals in the form of-avmplitude modulated carriers. Accordingly, the expression Vmodulating the-intensity as employed vin'the claims is intended to cover any well-known form of carrier modulation whether -it be amplitude modulation, frequency modulation, phases-shift 4modulation,` pulse modulation, carrier-shift modulation and the like.

What I claim isz' v l l. The method of recording signals on a moving magnetizable wire and the likeV which comprises, producing two crossed and displaced magnetic elds, varying said fields to produce a resultant field which has a component whichais Vinclined with respect to the axial movement of `said wire, and modulating said resultant iield by signals to be recorded.

2. The method of recording signals` in amovin'g magnetizable' wire which comprises-*generen ing a carrierl wave, modulating saidcarrierfwave by said signals-producing crossed magnetic fields under control of--said `modulated carrier while moving said wirev transversely' through said re;- sultant field to cause the recorded magnetic trace on the wire to follow a helical path on the periph- 3. A signal recording arrangement comprising 4a longitudinally movable Vmag'netizable 'wirc,

means-energized by signal modulated carrier wavesto produce crossed magnetic eldsfan electric phase displacing network for displacing the phase of the carrier Waves applied to one of said pair of means with respect to the carrier waves applied to the other of said pair of means to produce the eiect of a magnetic eld having a component revolvingV around the longitudinal axis of said wire but 4without physically revolving said means, said component being modulated to correspond with the signal modulations of said carrier.

A signal recording arrangement comprising a magnetizable wire, means to produce crossed magnetic fields varying at carrier frequency, means to move said Wire longitudinally through the resultant or said fields, means to phase-disone of said fields with respect to the other to cause said resultant to rotate around said wire, and means to modulate said resultant in accordance with trie signals to be recorded.

5. A signal recording arrangement comprising a magnetizable wire, a plurality of ield poles mounted adjacent said wire for producing crossed magnetic iields, means to energize said poles by a signal-modulated carrier Wave, said poles being displaced along the length of said 'wire a distance approximately equal to one-quarter the carrier wave length.

6. A eld coil arrangement for magnetizable wire recorders and the like comprising a plurality of pole pieces for producing crossed magnetic iields, a magnetizable recording wire longitudinally movable past said pole pieces, a source of signal modulated carrier waves and means to energize said pole pieces in time displaced phase at the frequency of said carrier Waves to cause the resultant magnetic field to have a heli-y cal trace with respect to the length of the wire.

7. In combination a ield coil arrangement for magnetizable wire records and the lille comprising ay plurality of magnetizable pole pieces for producing crossed magnetic elds, a magnetizable wire longitudinally movable past said pole pieces, a source of signal modulated carrier waves and means to energize one pole piece by said waves at approximately 90 phase delay with respect to the energization of the other pole piece to cause the resultant magnetic trace to follow a helical path around the periphery of said wire.

8. In combination a longitudinally movable and magnetizable recording wire, a pair of stationary opposed pole members between which the wire is movable, another pair of stationary opposed pole members between which the wire is movable, means to excite said first pair of pole members by a modulated carrier, means to excite the other pair of pole members also by said modulated carrier, and means `to delay the excitation of the second pole members with respect to the rst pole members to produce a magnetic trace which follows a helical path around the periphery of said Wire.

9. In a signalling system of the character described, a signal source, means to convert said signals into a signal modulated carrier, electromagnetic means to convert said carrier into a magnetic field having a rotating component which is modulated in accordance with the carrier modulations but without physically revolving said means, a magnetizable wire movable transversely through said field to produce a magnetic trace which follows a substantially helical path around the length of said wire, a magnetic pick-up past which said wire passes to translate the magnetizations into a modulated carrier signal, and means to detect the signal modulations in said translated carrier.

10. In a magnetic wire recording system, a magnetizable wire recording medium, said Wire being moved in the direction of its length, a source of signals of low frequency, a source of carrier wave oi relatively higher frequency, means for modulating said carrier wave in accordance with the signals from said first-named source, and electromagnetic means magnetically responsive to said modulated carrier wave for recording in said Wire a transverse magnetic iield rotating at an angular velocity substantially equal to the angular velocity of said modulated carriel wave, and without physically rotating said electromagnetic means.

In a magnetic wire recording system, a ferromagnetic wire of substantially circular cross-secticn, said Wire being moved in the direction ci its length, a source of signals of audio frequency, a source of carrier wave of supersonic frequency, means for modulating said carrier wave in accordance with the signals from said rst-named source, and electromagnetic means magnetically responsive to said modulated carrier wave for recording in said wire a transverse magnetic field rotating at an angular velocity equal to the angular velocity of said modulated carrier wave, and without physically rotating said electromagnetic means.

l2. In a magnetic wire recording system, a ferromagnetic Wire of substantially circular crcss-section, said wire being moved in the direction of its length, a source of signals of audio frequency, a source of carrier wave of supersonic frequency, means for modulating said carrier Wave in accordance with the signals from said first-named source, anda pair of recording electromagnets arranged in'space quadrature relation and electrically driven in phase quadrature relation by said modulated carrier wave, thereby to establish a magnetic field rotating at an angular velocity substantially equal to the angular velocity oi said modulated carrier wave, said ferromagnetic wire passing perpendicularly through said rotating iield.

13. In a magnetic wire recording system, a

ferromagnetic wire of substantially circulary cross-section, said wire being moved in the direction of its length, a source of signals of audio frequency, a source of carrier Wave of supersonic `frequency, means for modulating said carrier wave in accordance with the signals'from said first-named source, and a pair of recording electromagnets arranged in space quadrature relation and electrically driven in in-phase relation by said modulated carrier wave, said electromagnets being spaced apart along the length of said wire a distance approximately equivalent to one quarter the carrier wavelength, whereby to record in said wire a transverse magnetic ileld rotating at an angular Velocity substantially equal to the angular velocity of said modulated carrier wave.

WILLIAM E. BRADLEY.

REFERENCES Crrsp The following references are or `record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,245,286 Maszocchi June 10, 1941 2,351,009 Camras June 13, 1944 

